Surface tension is a property of liquids that allows their surfaces to resist external forces. It is caused by cohesive forces between liquid molecules at the surface that make the surface behave like an elastic membrane. Examples that demonstrate surface tension include insects walking on water and small droplets forming spherical shapes. Surface tension can be calculated using the formula F=S*L, where F is the applied force, S is the surface tension, and L is the length of an imaginary line on the surface. Surface tension is affected by temperature and impurities, decreasing with increasing temperature and increasing or decreasing depending on whether impurities are soluble or not.

1. z
Surface tension

2. • Surface tension is a property of the
surface of a liquid that allows it to
resist an external force.
• Due to force of attraction of liquid
molecules the free surface of liquid
behaves like elastic membrane or
rubber sheet.And this kind of tension
produce on surface of liquid.

3. Examples of surface tension

4. z
Examples by which we can understand the property
of surface tension
❑ The small insects are easily walking on the
surface of liquid.
❑ The small drop of water and mercury are in
spherical shape.
❑ A small niddle easily floats on the surface of
water due to surface tension

5. FORMULA
The force acting on the line is proportional to the length of the line.
Where, l= length of imaginary line
F= total force apply on line
Then,
F L F= S.L
S = 1 F
2 L UNIT is N/m
Dimension is [MT-2]
Or Surface tension,S = force
Length

6. z
Type of force act on surface tension:--
COHESIVE FORCE
➢ It is the force of
attraction between the
molecules of same
substance.
➢ This force is very strong
in solids , Weak in
liquids and extremely weak
in gases.
ADHESIVE FORCE
➢ It is the force of attraction
between the molecules of
two different substances.
➢ For example: Fevicol,gum
etc exhibit strong
adhesive property.

7. z
Application of Surface Tension
The property of surface tension is used
1. To prepare the ball bearings or bullets.
2. Use of detergent powder for washing the clothes.
3. The purity of water can be checked using the value of surface
tension.
4. Use of towel to dry our body after bath the towel absorbs water
due to capillary action.

8. z
Surface tension formula
T= rhdg
2cos0
Where,
T =SURFACE TENSION OF LIQUID
R =radius of capillary tube
H= height of liquid in capillary
D = density of liquid
0= Angle of contact
G= acceleration due to gravity

9. z
Effect of temperature and impurity
Effect of temp:- As
temperature increase the
surface tension of liquid
decreases and vice vera.
Effect of impurity:- If the
impurity is added in the liquid
and it is completely soluble
then surface tension of liquid
increases.
But impurities not
completely soluble then
surface tension of
liquid decreases.
Ex:- use of detergent powder
for washing the cloths.

10. DHANYAWAAD
Hope you get it
By : VIDHI JAIN